The Explosion of Strikeouts has Continued in 2013

K/9 (year, highest in any month)
2005 6.38 (6.49 - September)
2006 6.58 (6.86 - September)
2007 6.67 (7.05 - September)
2008 6.83 (7.10 - September)
2009 6.98 (7.12 - August)
2010 7.13 (7.33 - September)
2011 7.13 (7.48 - September)
2012 7.56 (7.79 - September)
2013 7.76

The lowest total from any month in 2012 was 7.36 in April, which made it higher than any individual month from 2005 to 2011.  The trend here is remarkable, but it obviously can't continue going up like this forever.  It does not seem at all ridiculous to assume that pitchers could average over 8 strikeouts per 9 innings for an entire month and then an entire season. 

Why is this happening?  This article from Tyler Kepner in the New York Times before the season started discusses several different possibilities, one of which is increased specialization in the bullpen.  As more and more great pitching prospects are placed on a path early on in their careers to be a bullpen strikeout specialist, we will see more astonishing seasons.  In 2012, there were 4 pitchers (Craig Kimbrel, Aroldis Chapman, Kenley Jansen, Ernesto Frieri) with at least 60 innings and a K/9 average of over 13 (there was a total of 9 between 2000 and 2010). 

Starters; Relievers
2005: 6.04; 7.10
2006: 6.21; 7.29
2007: 6.29; 7.36
2008: 6.44; 7.53
2009: 6.64; 7.61
2010: 6.76; 7.85
2011: 6.74; 7.90
2012: 7.12; 8.40
2013: 7.27; 8.57